Mirrors, particularly large mirrors for household use such as wardrobe mirrors, are subject to breakage and shattering when struck. Obviously, the risks to persons positioned near the mirror when it breaks are great if the glass is allowed to shatter and fly apart, and the resulting debris is difficult to clean up without injury. In order to protect the users of such mirrors, an adhesive backing material is provided to the mirror which prevents the glass from shattering if the mirror is broken. This adhesive backing material holds the glass together for a sufficient period to facilitate disposal thereof.
Backings for such mirrors commonly are tested by allowing a suspended object of a predetermined weight to be swung from a given distance against a mirror disposed in a generally vertical orientation. The larger the weight, or the greater the given distance, the greater the amount of force the backing must withstand to prevent the glass from shattering. Most existing adhesive backings used for such purposes will withstand only a 100 foot/pound test and are incapable of withstanding a 400 foot/pound test. In a 100 foot/pound test, a 100 pound weight is suspended from a point above a vertically oriented mirror and is allowed to swing about the point towards the mirror from a distance of one foot. In the 400 foot/pound test a 100 pound weight is allowed to swing towards the mirror from a distance of four feet. If the mirror breaks and the backing tears or separates more than six inches, allowing the glass to fly apart, the backing has not withstood the required test.
Most such backings presently used are dispensed as an adhesive tape from a roll. Such tapes are generally formed as a single layer of polyethylene having a pressure sensitive adhesive disposed on one side thereof.